Warming Signs: Different Fish to Fry

Often, when we talk about climate change, it seems like a far-off scenario. We talk in terms of saving the planet for future generations and predict disruptive sea level rise within the century. But the effects of climate change are already felt around the world; future changes will only intensify them.

Close your eyes and imagine an underwater world teeming with brightly colored fish and rich coral. When you’re done peeking into that seascape, you head to the dinner table and feast on fresh tropical fish. Look around: Do you see turquoise waters lapping against the shores of an island in the Caribbean or the Pacific? Or are you surrounded instead by the often-frozen coastlines of the Arctic?

In the last century, the North Atlantic ocean has warmed by at least two degrees; other oceanic “hotspots” have seen a rise of three degrees. That may not sound like much, but in delicate oceanic ecosystems, it means the world.

In a few decades, Arctic and Antarctic seas will likely be home to some of the most diverse and flourishing marine populations on the planet, while regions closer to the equator will see a rapid deterioration of sea life. As oceans respond to wide scale climate change, marine life is changing faster than many of us can keep up.

You don’t have to go to the tropics or the Arctic, though, to see how climate change is already affecting fish—and those who depend on them for food.

What Climate Change Means for Marine Life

There are, of course, other reasons for changes in fish populations, overfishing and habitat loss chief among them. And it’s unclear whether the fish themselves are swimming to new areas as part of a mass migration, or whether a few fish have simply thrived better in the new waters and reproduced more.

Up to two-thirds of marine species have changed their migration and egg-laying behavior in the northeastern United States—including lobster, whiting, black sea bass, mackerel, herring, monkfish and others.

Keep in mind, of course, that our oceans are one of the last unexplored frontiers in our world; we know more about other planets than we do about our deepest waters. In fact, scientists only know of about 200,000 marine species, which they estimate to be only 10% or so of the marine biodiversity on Earth.

So, as warmer waters evict many of these marine creatures and force others into their habitats, it’s quite difficult to predict how they will affect very complicated ecosystems in their new homes. However, scientists are trying to monitor these changes as quickly as they happen, in order to predict how they will affect ocean life.

New Predators, New Prey

When fish move to new waters, the ecosystems can change dramatically due to more competition for resources—and to new dinner patterns among the fish themselves. Tropical species moving into the waters around Japan, Australia, the Mediterranean, the Gulf of Mexico and the Atlantic coast are munching away on kelp forests and sea grass. If a fish mows down all of the kelp or sea grass in an area, the animals that take cover in the grass need to find a new home.

Not all fish are moving because of a changing environment; some, like a species of Alaskan char, are simply following their normal prey, salmon, as those fish move north.

Eventually, fish won’t be able to go any further north. Those already living in the coolest waters on the planet will dwindle as the water warms and new fish move into town.

And not all of those newcomers will fit into their new neighborhoods. To go back to cod, for instance: the global population of cod could be cut in half in the next 30 years. Fish like cod might not interact well with their new compatriots. In fact, cod create sounds with their swim bladders in order to attract mates—and scientists say they have regional accents that make it difficult to be understood in new regions. It’s like walking into a British bar and not understanding a blimey word.

Moreover, fish aren’t the only marine animals. For instance, a decline in Arctic fish could very well devastate populations of seals and polar bears, which depend on those fish to survive. It’s the same in Antarctica: seals and penguins would have to make major modifications to their diets in order to survive without their usual food.

Fishy Diet Changes

But all that’s fish food—what about our own changing diets?

Coastal countries close the equator depend heavily on fishing, and the polar migration could have devastating consequences upon the economy and food security of countries already deeply stressed by climate change.

Three billion people around the world rely on fish for their daily or weekly meals. On small islands and in coastal nations, many of which are still economically developing, marine life makes up half of the diet.

These are also the countries that will be hardest-hit by climate change. Half of those meals may simply swim away for cooler waters—leaving those whose diets and incomes depended on them to join the one billion people on earth who already don’t have enough to eat.

In order to survive, these regions must adapt to the changes quickly. It may be one of the greatest challenges facing these countries this century. But if the fish can change, so must we—at least until we find a way to halt ocean warming.

Researchers at the Centre for Environment, Fisheries and Aquaculture Science (CEFAS) have been monitoring sea around the UK for more than 100 years, and recently they’ve seen a big shift away from their former staple, cod, and toward squid as waters continue to warm.

“Twenty or 30 years ago we hardly saw squid in our surveys,” Dr. John Pinnegar of CEFAS told BBC. Now, two-thirds of research stations around the North Sea are seeing the cephalopods regularly.

Right now, all this squid is being shipped to other countries. But, Dr. Pinnegar says, food habits in the UK may change to accommodate new kinds of seafood. Eating local may soon involve previously exotic dishes.